Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$33.94	6.760%	$36.2343	$36.23	$36.25	$36.20
Purchase #2	$79.42	5.240%	$83.5816	$83.58	$83.60	$83.60
Purchase #3	$64.66	11.795%	$72.2866	$72.29	$72.30	$72.30
Purchase #4	$195.89	12.192%	$219.7729	$219.77	$219.75	$219.80
Purchase #5	$190.60	4.755%	$199.663	$199.66	$199.65	$199.70
Purchase #6	$187.48	8.695%	$203.7814	$203.78	$203.80	$203.80
Purchase #7	$88.92	11.630%	$99.2614	$99.26	$99.25	$99.30
7 purchase totals =	$840.91		$914.5812	$914.57	$914.60	$914.70